On 07/02/20 07:02, Ram Ramesh wrote:

I got no response on this and want to take a shot before going the
backup way.

Assuming (hda1 and hdb1 in raid1 md0) Will the following work?

1. Fail and remove hdb1
2. Create new RAID1 md1 with hdb1 and missing
3. dd md0 onto md1

I wouldn't bother with any of the above. Just shut down and physically
remove a LIVE disk. That now is your backup.

In fact, this might be a good excuse to get a 3rd disk and either go
raid 5 or use it for backups.

4. Make both bootable. (I suppose I need to change UUID of md1
   partitions. I suppose that is easy)

Yes it's easy. Yes it should have been done a LOOONG time ago.

5. Boot both and double check

They'll be degraded, so you might have to do a forced assembly to make
them run ...

6. Now upgrade md0 without fear.
7. Boot and test the new system for a couple of days to make sure
   everything is fine.
8. If that fails, delete md0, and add hda1 to md1. If not delete md1
   and add hdb1 to md0

Yup.

Regards
Ramesh

Cheers,
Wol